Respirable gas administration apparatus



Dec. 1, 1959 A. s. J. LEE

RESPIRABLE GAS ADMINISTRATION APPARATUS 2 Sheets-Sheet 1 Filed May 18,1956 mUdDOm mdnmmmda MUKDOW 5535;

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Dec. l, 1959 A. s. J. LEE

RESPIRABLT: cAs ADMINISTRATION APPARATUS Filed may 18', 195e 2Sheets-Sheet 2 xNvEN-roR ARNOLD S. J. L EE BY @MMM H IS ATTORNEYS Thisinvention-relates `-generally to apparatus for ad- -ministering arespirable gas to a living subject, animal or human. More particularly,the invention relates to apparatus of this character adapted 4toautomatically exert `a form of control over the gas to therebyautomatically render a bodily state of functioning of the subject inaccordance with apre-selected standard therefor.

This-application isa continuation-in-part of my co. VpendingapplicationSerial No. 484,460 iiled lanuary27,

`In connection `with the description of the present invention, unlessthe .context otherwise requires, the following words andphrases Yare tobe taken in the senses indicated as follows. The phrase respirable gasis used to denote `a fluid substance which may be an anaesthetic,

therapeutic'or-experimentalpure gas or mixtures of gases Aand/onvaporsand/or gas-borne suspensions of liquid and/ or solids. A respirable gasof any of these sorts will be referred to as an input gas. when subjectto inhalation by the patient, and asan output gas when the consequenceof exhalation by the subject. More specifically, output gas will referto that portion of the'breathed out gases from the lungs of a patientwhich is last breathed out just before the patient starts to breathe inagain; that is, the gaseous contents of the lung which were in intimatecontact with the blood. In speaking of a property or properties ofgagas, the Word property is used to denote one or more of the sum total ofthe characteristics of the gas Whichserve to identify the givengas bydifferentiating it'from all other gases. A referred to'property ymaybephysical or chemical in nature and may either represent a simplecharacteristic or a composite of characteristics which are all physical,Vall chemical or part physical and part chemical. i

As further considerations, the Word analyze is used to denote the actionof continuously or semi-continuously measuring somel substance in .orderto determine the value of one or more vproperties thereof. Also, theword automatic is usedto denote continuous or semi-continuous operationof a device yor system, essentially without the intervention of a humanoperator. The bodily state of functioning of a subject is to be taken tomean what is either usuallyjconsidered `a bodily .function fsuch as rateof respiration or a bodily condition such as depth of anaesthesia, `ordegree of lbalance between oxygen intake and metabolism.

While from the above it will be seen that the purview of thepresentjinventon comprehends a wide variety of forms o'f respirable gasadministration apparatus, for convenience the shortcomings of the priorart in this field will be discussed in connection .with that form ofsuch apparatus which is used to produce anaesthesia in a living subject.y The usual form of anaesthetc Iadministration apparatus depends upon ahuman operator for its control. In operating the apparatus theanaesthetist conventionally must .rely entirely upon the data 4`directlypresented to his 2,915,056 "'atentedDec. 1, 1959 Vsenses in theformo'f-external symptoms manifested by depth deemed desirable inview yofthe circumstances, the `'.anaesthetist,corrects for this discrepancy bymanipulating his apparatusto change the current depth of anaesthesia inthe appropriate direction.

From the above it will be seen thaty a number of'factors may enter intothe operation of a human controlled anaesthetic Vadministrationapparatus torender this operation an unreliable onefor reaching theresult desired. One such factorarises outof a possibly incompleteilow ofdata from 4the external. symptoms of condition manifested by the subjectto the sense receiving organs of the anaesthetist. Another such factorproductive of unreliability may reside in theinexperience orotherpsychologicalinability of the anesthetist to correctly interpretthe sense data received by him. A third such factor which should bementionedis thertotal time-lag occurring between the time that anincorrect depth of anaesthesia .-iirst'occursand the time When'.thedepth is brought back fully to its desired value. This total time lagrepresents an accumulation of the respective times necessary forthe-incorrect depthof `anaesthesia to'be first manifested asanexternalsymptom by the subject, the time necessary for the anaesthetistto iirst observe this symptom, the timerequire-d for interpretationofthe symptom in the mind `of the anaesthetist, and the time required,after the-anaesthetist, has reached his `mental conclusion of the propercorrective measure, 'for the anaesthetist to manually carry out thiscorrective measure. lt will be seen that the factors contributing tothis total time lag each represent an inherent slownessof response ofthe hu- `man body or brain, and that hence the time lag is unavoidableinfthe conventional anaesthetic administration technlque.

It has been proposed heretofore to circumventthese shortcomings byproviding anvautomatic anaesthetic administration system. This prior artsystem, however,.is designed to determinethe depth of 'anaesthesia ofthe subject by means of electric signals which are generated eitherwithin the body of the subject or as the result oi a direct sensing, byprobes or the like in contactwith the body of the subject, of the bodyfunctioning of the subject. Thus, the mentioned prior artsystem-proposes to use electro-encephalographic or electrocardiographicsignals as indications of the depth of anaesthesia of the subject. Thesesignals are in themselves complex in form, and, moreover, the functionalrelation between the signals and the depth of anaesthesia is relativelycomplex. Accordingly,A it is necessary in the mentioned prior art systemto have an unusually complicated system of electric circuits andelectronic tubes. This large-scale electrical organization is, ofcourse, undesirable because of the expense, bulk, liability to failure,and difficulty o'f maintenance involved.

It is accordingly Van object of the invention to pro- .vide respirablegas administration apparatus which is lfree of the disadvantages notedabove.

Itis another object of this invention to provide apparatus of the abovenoted character which operates by virtue of a relatively simpleindication of the bodily state of functioning of the subject.

A further object of the invention ,is to provide `apparatus of 'the`above noted character .requiring a `minimum number of electric circuitand other organizational components.

These and other objects are realized in accordance with the presentinvention by providing a uid flow system carrying alternate ow of inputand output gas to and from a living subject, and by providing anadjustable gas regulator mechanism connected in this system inregulating relation with the input gas to exercise a form of controlthereover affecting the bodily state of functioning of the subject.Further, a gas analyzer means is connected in the mentioned fluid Howsystem in responsive relation with the output gas to automaticallyanalyze the same by a mode of analysis providing signals indicative ofthe bodily response of the subject to the input gas. The signals sodeveloped by the analyzer means are received by an automatic meanswhich, responsive to these signals, adjust the regulator mechanism toautomatically control the input gas to render the bodily state offunctioning of the subject accordant to a preselected standard.

The invention may be better understood from the following detaileddescription of typical embodiments thereof, taken in conjunction withthe accompanying drawings, in which:

Fig. l is a schematic diagram of a respirator-anaesthetizing apparatusconstructed according to the invention;

Fig. 2 is a diagram of details of the apparatus of Fig. 1; and

Fig. 3 is a schematic diagram of an anaestheti'c administrationapparatus constructed in accordance with the invention.

In the description to follow it will be understood that analogouselements in the two embodiments will be designated by the same number,with such elements in the second embodiment being further designated bya prime sux for the number. Further, analogous elements in the sameembodiment will be designated by the same. number with different lettersuffixes.

Referring now to Figs. 1 and 2 which show a respirator-anaesthetizingapparatus for inducing forced breathing of a living subject along withadministration of anaesthesia thereto, as a part of the apparatus thereis shown a fluid ow system permitting alternate ow of input and outputgas to and from a subject during, respectively, the inhalation and theexhalation phase of each recurring respiration of the subject. Morespeciiically, this uid flow system includes a gas distributing manifoldhaving an inlet port 11, an outlet port 12, and an exhaust port 13. Anadapter 14 is coupled to manifold 1t) for the purpose of guiding gasbetween the manifold and the respiratory tract of the subject.

The inlet port 11 has connected thereto a tirst conduit means comprisedof apair of conduits 20, 21 respectively communicating with sources (notshown) of anaesthetic gas (as, say, nitrous oxide at 50 p.s.i.) and asource of oxygen (at, say, 50 p.s.i.). The mentioned conduit means isalso comprised of a third conduit 23 coupled directly at one end withthe inlet port 11 and coupled at the other end through a mixer 24 withthe conduits 20, 21.

The conduits 20, 21 in the usual manner have respectively interposedtherein the manually set pressure regulators 26, 27. Each of theseregulators is adapted to accept gas at high pressure from the sourcecoupled therewith by way of the conduits, and to deliver this gas atsome lower preset constant pressure essentially independent of the rateof gas flow. For indications of this lower preset pressure, the conduits2i), 21 are respectively equipped with the pressure gauges 28, 29.

.The mixer 24 is a conventional gas ow device for mixing two gases in aconstant preset proportion essentially independent of the rate of flowof the mixture of the gases. Thus, from the input of nitrous oxide andoxygen respectively received from the conduits 20, 21,

the mixer 24 is adapted to flow into conduit 23 an anaesthetic mixtureof fixed composition as, say, 70% nitrous oxide and 30% oxygen. Byvirtue of the construction of mixer 24, the percentage composition ofthis intermixture remains constant irrespective of pressure changes inconduit 23.

To provide for control of the input gas, the conduit 23 has interposedtherein a variable regulator mechanism 30. In the present instance theinput gas is controlled with regard to the specific property of thepreslsure thereof, and hence the regulator mechanism 30 is a variablepressure regulator which is adjustable in its regulating action byappropriate movement of a controller arm 31. In essence, the variablepressure regulator 30 receives gas owing at medium pressure throughconduit 23 from mixer 24, the regulator delivering this gas at somelower pressure determined by the position of control arm 31. Thedescribed regulator may be of the type commonly employed on acetyleneand oxygen tanks for welding purposes, the regulator control arm beingadapted to motor drive. The lower pressure output gas from the regulatoris delivered into conduit 23 for flow thereof to inlet port 11 and fromthence through manifold 10, adapter 14, and into the respiratory tractof the subject. For convenience in measuring the pressure of theregulated input gas, the portion of conduit 23 between regulator 30 andinlet port 11 may be equipped with the pressure gauges 32, 33 adaptedrespectively, to give exact pressure readings over a limited scale andapproximate pressure readings over a wider scale.

The outlet port 12 has connected thereto a second conduit means in theform of a conduit 40 running between the outlet port and an exit 41permitting venting of gas in the conduit to the atmosphere. The conduit40 has connected therein a gas analyzer means 42 (to be later describedin further detail) and a sampling means 43 disposed in the conduitbetween the gas analyzer means and the outlet port 12. The samplingmeans in its essential components comprises a collapsible, but somewhatstift' and resilient tube 44 (fabricated from say, rubber), a largerdiameter rigid tube 45 enclosing the major extent of tube 44 in apressure-tight chamber, and valve means in the form of a check valve 46disposed in conduit 40 between manifold 10 and tube 44 to permit ow ofgas in the conduit only from the manifold towards the analyzer 42. Thesampling means 43 may also desirably include a second check valve 47disposed in conduit 40 between tube 44 and analyzer 42 to preclude anysubstantial backward iiow of gas from the atmosphere through the exit 41and thence into the analyzer.

As stated, the presently described apparatus is in part a respiratorapparatus adapted to produce forced breathing in a subject. To this endthe apparatus is provided with a two-way breathing valve wherein a valveplug 50 is adapted to be reciprocated back-and-forth between an upwardseated position covering the exhaust port 13 and a lower seated positioncovering the inlet port 11. In this reciprocation the valve plug 50 ismoved downwardly by a spring 51 disposed above the plug to act incompression thereagainst from a xed support for the spring.Conveniently, the spring 51 may be positioned within an exhaust conduit52 leading from exhaust port 13 to the atmosphere, the fixed support inthis case being in the form of a bracket 53 extending radially inward ofconduit 52 to hold the spring in alignment with the axis of the conduit.For better guidance of valve plug 50 in its reciprocating movement,preferably the compression spring S1 encircles an upper guiding stem 54which extends from a juncture with plug S0 upwardly through bracket 53by way of a bore (not shown) therein serving to constrain the stem to upand down movement only.

To provide upward movement in reciprocation of the valve 50, a fluidpressure cylinder 60 is mounted by an internal bracket 61 within and inalignment with the axis of a vertical section of conduit 23 adjacent tothe inlet .frptfV 1 1. cylinder l6th-containswithinv itsbore; a-,pistonE1.62` connected to the `valve plug :.50 :by` alowen valve stem ,163.Thus,-intthe presence of increased pressure inicyl- ,inder 60,suflicient force willbeexertedon thelpiston to drivevalve plug 50against thecompression of springiSl 1 ygtoan upwardly seated positionsealing exhaust `port 13. .t Conversely, when the pressuregin cylinder60 is per- @mitted to decrease, the ccmpressivefforce `of spring 51overcomes the upwardly directed `piston-force. Accordingly, both valveplug 50 and-piston62fare driven downward with the respectiveconsequences that the plug is seated to seal off inlet port-lLwhiletheinterior of cylinder is emptied of fluid by the downward movementof thepiston.

Reciprocation of the described breathing valve isv established by atiming means (Fig..2) comprised of a constant speed motor 70, abreathingcontrol cam 71a and sampling control cam 71b commonly driven bythe motor- 70, and a breathing controlA slide vak/e720:V and sarnplingcontrol slide valve '72b actuated, respectively, from the cams 71a and71b. Since the two valves mentioned are essentially similar inconstruction, it is only necessary ,for the most part to describe slidevalve 72a, it being understood, that, unless -otherwise noted, thedescription of a given number element in valve 72a applies as prop-`erly to ,the element designated by the same number in valve 72b.

The slide valve 72a comprises a cylinder 75a,\a piston 76a, slidable intight-fitting relation within this cylinder,

j a cam follower 71a mounted on piston 76a to ride on cam 77a .tothereby translate the .variation in contour vthereof into up and downpiston movement, and a compression spring 78a acting on 4piston 76a tomaintain cam follower 77a in iirm contact with its cam. Within cylinder75, the piston 76a is cut away -circumferentially tohave formed thereinanannular groove 79a. The groove 79a performs the function of furnishinga fluid ow coupling between either a middle conduit 85a and a lowerconduit 86a coupled to a high pressure uid source, or between the middleconduit 85a and anupper conduit 87a venting to the atmosphere. Themiddle conduit 85a is itself coupled with the interior of drivingcylinder 60 for the breathing valve.

As` stated, the sampling control valve 72b is essentially similar inconstruction to the breathing control valve 72a with the followingexceptions. First, the cam 7117 which operates valve 72b is of differentcontour than the cam 71a for valve 72a. Second, in valve 72b it is theupper conduit 37b which is connected to the high pressure fluid source,and it is the lower conduit 86a which opens to the atmosphere. Third,the middle conduit 85b of Valve 72b furnishes a iiuid ilow coupling fromthe valve to the interior of the outside tube 45 (Figures 1 and 2) inthe sampling means 43.

Considering for the time being the `action of breathing control valve72a only, the contour of the cam is subdivided into a lowered arc 90 ofsmaller angular extent and a raised are 91 of larger angular extent.When cam follower 77a rides in lower arc 90, the piston 76a YVpositionsgroove 79a to provide for flow of high pressure 'uid from conduit 86athrough conduit 85a lto the interior of cylinder du. The valve plug 50will be accordingly moved upwand to uncover inlet port11 and to sealexhaust port 13. Responsive to this valve plug movement, a ow of inputgas under slight pressure will ensue from conduit 2,3 into manifold loand from thence through adapter 14 into the respiratory tract of thesubject. Within the respiratory tract, the slight pressure of the inputgas causes the subjects lungs to expand, the net effect being aninhalation by the subject which is forcibly induced. I

The changeover from inhalation to exhalation in the Auforced respirationof the subject is effected by rotation of the yearn 71a raising the camfollower 77a up upon the arc .'91 of the cam contour. Piston 76a isaccordvingly moved-upward to 'disconnect `heginterior ofcylin- .der 60(Figujrelyffromlthe uidppressure conduitv'da (Figure v2);an,d`-to1establish` an exhaustpath for the cylinder thronghconduit8,5,z,:valveg groove 79a, and ex- 10'are respectivelyuncoveredand,sealed. With the respective changes in condition takingplaceastorthese two ports, the lungs of the-subjectfare freeof the pressureeffect ofthe input gas. Freed of this pressure .,efect, `the'subjectslungs contract `elastically to exhale output gas through adapter14,f-manifold 10, exhaust port 13, and exhaust conduit 52.

-lt is thus seen that theqdescribed apparatus develops recurring forcedrespirations of Ythesubject consisting alternately., ofinhalationsand-exhalations. An apparatus performing this functioniscommonly used, for example, where for medical reasons it is desirableto anaesthetize da subject who has been completely paralyzed by theaction of a drug or the like. Y

It is well known, in the normabphysiological control of respiration,that the `amount of lair. taken into a subjects lung is'so adjusted bythesubjects body that the carbon dioxide level remains constant at thesubjects physiological level. The Ycarbon dioxide normally presentexerts a tension of 40mm. of mercury. vThis -amount of air is thenusually adequate to provide a proper voxygen availability to the bloodinthe subjects lungs.

In natural respiration, this amount of air taken in is ordinarilycontrolled by a physiological process wherein involuntary nerve centersof the human body respond `to the percentage of carbon dioxide in theblood stream `to adjust the rate and/ or depth of respiration. Thus,where the carbon dioxide in the blood stream increases, the mentionednerve centers act to increase the involuntary `depth and rate ofbreathing or to createafeeling oi shortness of breath in the subject.Also, when the carbon dioxide inthe blood streamdecreases, the mentionednerve centers adjust .the involuntary `breathing of the subject to theproper rate, and depth.

It will be evident, however, thatwith complete paralysis of the subject,the described involuntary self-adjustment of the state of bodilyfunctioning of the subject is `no longer effective because of paralysisof the lungs. Unless the carbon dioxide tension is carefully controlledby accomplishment of the required tidal exchange,vimpor tantconsequences result. Thus, reducing the alveolar tension to say 2O mm.mercury induces a general vasoconstriction, especially in the cerebralblood vessels and diminishment of the respiratory drive as therespiratory center is made less sensitive. Still lower carbon dioxidetension, such as l0 mm. of mercury, produces syncopy or fainting. Highercarbon dioxide arterial blood tensions than normal, such as about `50mm. of mercury, cause increased respiratory drive, dilate the cerebralblood vessels, and often cause increased blood pressure and pulse rate.It is, accordingly, necessary that some artificial substitute beprovided for the involuntary control over respiration normally providedwithin the body of the subject when the subject is anaesthetized.

In accordance with the present invention, to provide for this substitutecontrol over respiration, the cam 71b is shaped in contour to haveradially raised and lowered portions lill) and 101 which arerespectively of such angular extent and phase with respect to thecontour of cam 71a (which establishes the periods of inhalations andexhalations) that the cam follower 775 rides on lowered arc 101 onlyduring a short intervalat the end of each exhalation. Thus, during amajor interval of a respiration induced in the subject, the piston '76bof the sampling control valve is positioned upward to establish a uidflow coupling from pressure conduit 87h through valve groove 79h andconduit SSbto the interiorof 7 the outside tube 45 of sampling means 43.In consequence, there is produced within this outside tube a highpressure condition which collapses the inner tube 44 during inhalationby the subject and during most of the time of exhalation thereby. At theend of exhalation, however, the cam follower 7712 drops momentarily intothe lowered arc 101 of cam 71b with the consequence that piston 76bdrops downward to vent the interior of tube 45 to the atmosphere throughconduit 85h, valve groove 79b and exhaust conduit 86b. With the pressurewithin tube 45 so released, the inner tube 44 springs back intouncollapsed shape to thereby produce a vacuum in i-ts interior.Responsive to this vacuum, the check valve 46 opens to permit a sampleof end-of-exhalation output gas to liow from manifold 10 to within tube44. When,

aty the beginning of the next inhalation, the cam follower 77b is onceagain raised up on the arc 101 of cam 71h, the resulting higher pressurecondition re-established -within tube 45 causes the tube 44 to againcollapse to thus force the contained sample of end-of-exhalation outputgas through the check valve 47 to fiow through the analyzer 42.

As is known, over the whole interval of an exhalation, the carbondioxide content of the output gas undergoes a wide fluctuation in value,the spread in values in this fluctuation not being of substantialsignificance as a measure of the carbon dioxide level in the blood ofthe subject. Considering the succession of individual fluctuationsoccuring from exhalation to exhalation, however, there may be discernedtherein a trend in value representing a measure of the carbon dioxidecontent of the blood stream. The course of this trend may be establishedin various ways, as by taking the average value of each fiuctuation orthe highest value thereof, or the lowest value thereof, or the valuethereof at some fixed phase in time of the exhalaton period. It has beenfound, however, that a very satisfactory measure is obtained of richnessof the blood in carbon dioxide if a sampling means like that describedis utilized to sample the output gas by taking end-of-exhalation samplesthereof which are, of course, alveolar gas. Since no carbon dioxide isadministered, it has a zero concentration in the input gas. Therefore,the difference between arterial carbon dioxide concentration and venouscarbon dioxide concentration will be small, even when there areappreciable areas of atelectasis. The carbon dioxide output gas tensionaccordingly will about equal the arterial blood carbon dioxide tension.Since the output gas, i.e., the last portion of the expelled or alveolargas, normally has a carbon dioxide tension of 40 mm. of mercury thearterial tension in carbon dioxide will be about the same figure.

The output gas samples which pass through analyzer 42 are analyzedtherein for the specific property of the output gas of its carbondioxide content. Preferably the analyzer 42 is in the form of aninfra-red spectrophotomer analyzer such as is described in furtherdetail on pages 1021 and 1036 of Medical Physics, Volume II, by OttoGlasser and published by the Yearbook Publishers, Inc., Chicago,Illinois. An analyzer of this type is adapted to provide on an outputlead 165 an electrical voltage signal which is roughly proportional to(or, at least in direct correspondence to) the percentage of carbondioxide in the gas mixture fed to it. For the purpose of generating suchsignal, the analyzer has a selfcontained amplifying system.

The analyzer signals on lead 105 are fed to an automatic means whichresponds to these signals to automatically adjust the setting of ormaintain a given setting of the variable pressure regulator 30. Thisautomatic means may take the form in a broad sense of a means forgenerating a reference signal representing a preselected Value for theend-of-exhalation carbon dioxide content of the output gas (and thus apreselected value for the richness of carbon dioxide in the bloodstream), a means for comparing the analyzer signals in value with thisreference signal, and a means responsive to a change in value of theanalyzer signals away from the reference signal for adjusting thepressure regulator 30 to ultimately cause the analyzer signals to followthe reference signal. While the reference signal may, of course, be asignal which changes in value over time in a preselected manner, in mostcases it suffices for the referenceV signal to have a steady value overtime in the absence of manual intervention to change the value of thesignal.

As a specific example, the automatic means referred to may take the formshown in Figure 1 wherein the reference signal is generated as thesteady voltage output of a reference signal generating means 109. Thismeans may take such form that the output thereof appears on a movabletap of a potentiometer resistor 111 connected across a voltage sourceshown as the battery 112. As stated, this reference signal represents apreselected value for the end-of-exhalation carbide dioxide content ofthe output gas, the signal thus being indicative of a preselected valuefor the richness in carbon dioxide in the blood stream of the subjectbeing administered to by the apparatus. Selection of such value or achange in the selected value from one to another value is effected bymanually sliding tap 110 over resistor 111. A meter 113 may, forconvenience, be connected with a signal carrying lead 114 from tap 110,the meter indicating the voltage of the reference signal.

The analyzer signals on lead 105 and the reference signal on lead 114are fed as respective inputs to a servo system such assay, aservo-system comprised of the components manufactured by the BrownInstrument Division of the Minneapolis Honeywell Company of a continuousbalancing amplifier (catalog number 351921 and a balancing motor(catalog number 767504). As shown in Figure 1 this servo system iscomprised essentially of a servo amplifier 119 (consisting 'of asubtracting chopper amplifier 120, and a power amplifier 1'21) and aservo motor 122 in the form of a two-phase induction motor characterizedby a first phase winding 123 and a second phase winding 124 which isspatially in quadrature relation with phase winding 123. The phasewinding 123 may be energized in a conventional manner from analternating current power source 125, which also acts, as will now bedescribed, as a synchronizing signal source for the subtracting chopperamplifier 1120.

The subtracting chopper amplifier is of a Well known type, which, in thepresence of a difference in voltage between the analyzer signals and thereference signal inputs, is adapted to produce an error signal form ofthe analyzer signals. This error signal represents by its amplitude andpolarity the amplitude and polarity of the voltage difference betweenthe input analyzer and reference signals. As another function, thesubtracting chopper amplifier 120 is adapted to render this error signalof alternating form by chopping the error signal at the frequency andphase of a synchronizing signal received by the amplifier. In thepresent instance, this synchronizing signal is a signal originating withalternating source 125 which is thereafter impressed with a 90 phaseshift by a phase shifting device 126. Accordingly, if there is nodilference in voltage between the analyzer signals and reference signalinputs to amplifier 120, the amplifier will produce zero output. On theother hand, a voltage difference between the input signal will berepresented at the output of the amplifier by an alternating errorsignal of the same frequency as the current which excites phase winding123. In dependence on Whether the analyzer signals are greater or lessthan the reference signal, the error signal output from amplifier 120will have one or the other of opposite phases, both of these phasesbeing electrically displaced 90 from the phase of the current energizingwinding 123.

The error signal output from amplifier 120 is fed to 19 ilfirepower-amplifier 121 which-.amplifes 'the signalbysan t amountsuicient toprovide forproper energization ofthe :phase .winding 124theamplied error 1signal being applied to this winding. AAs` is known, themotor 122 :rwillnot rotate when only phasewinding 123 is energized. 1

.In the presence, however, of an error signal which'energizes winding124 in 90 phase relation to the current inwinding 123, the motor 122will rotate in one direction of rotation or the other in dependence onwhether the @error signal leads or lags by"90i the exciting current for.Winding 123.

.The mechanical angular output of motor 122`is couipled to the controlarm 31 of pressure regulator 30 .by a linkage consisting of the arms 128and 129. .There is I thus established in the respirator apparatus aclosed loop ttcausal sequence wherein a series of responses are inter-Arelated as follows:

'i If ythe quantity of gaseous intake by the subject'is lower thanoptimum, this fact is manifested in the physiological functioning of thesubject by an increase inthe` vvhale more deeply, the carbondioxide-content of the sub-H jectls blood stream is diminished until theproper balance is once again restored between vthe quantity ofgaseousintake and the carbon dioxide level of the subject. Conversely, ifthe-quantity of gaseous intake by the subject is greater than optimum,the carbon dioxide content of this blood stream drops to create adifference between the analyzer signals and the reference signal to thusstimulate t thedescribed servo system to adjust vthe regulator 30 todecrease the pressure of the input gas fed to the subject.

As la result, the forced respiration of thesubject will be2 less deep,and the carbon dioxide content ofthe blood stream will rise to itsproper level.

By means of this invention actual` tests have` maintained arterial bloodcarbon dioxide tension within 3 mm.

of `40 mm. of mercury, the normal tension, for aslong as three hoursduring surgical operations.

kInstead of controlling respiration on the basis of carbon dioxide, thesame thing may be accomplished by analyz- `ing the oxygen content of theoutputgas and adjusting .jthe oxygen or air given to the patient tomaintain a normal arterial oxygen tension of about 105 mm. of mercury.The alveolar gas oxygen tension is normally about V110 mm. of mercury.The gradient between arterial and .alveolar oxygen tensions isordinarily about mm. of mercury although errors in ventilation ordilfusion may make for increases in the gradient. For the purpose ofIcontrolling respiration by oxygen analysis it is convenient to base therespiration control system on the normal venous oxygen tension of 40 mm.of mercury. Using this as Athe standard, a sample of output gas taken atthe end of exhalation may be analyzed for oxygen content, cornpared withthe standard and the input gas adjusted accordingly to maintain properadministration of oxygen. uIn such a system it is generally desirable tomaintain an `input oxygen tension of below 250 mm. of mercury sincenonrapparent errors may arise `due to the characteristics ofhemoglobin-oxygen dissociation.

1"Referring now to Figure 3, there isshown therein another example ofthe present invention in the form of an apparatus for administeringanaesthetics to a subject. In this apparatus a manifold 10' has an inletport 11',and an outlet port 12', and has joined therewith an adapter'.14' in the form of a mask .which fits over thenose .and mouth of thesubject. The adapter 14', asv before,y performs the lfunction offurnishinga guidewayforafow of I zfgasfbetween manifold v10' and Itherespiratorytract =of the subject.

Coupled with the inlet port 11' is a first conduit means vconsisting of.the separate conduits 20', 21', respectively 1 coupled to a source. ofanaesthetic gas (as, say, cyclopropane) at above atmospheric pressureand a source of oxygen at above atmospheric pressure. The first-con-4,duit :means is also comprised of a mixing conduit v coupled between agas flow junction 131 and a junction of the conduits 21', 20', a conduit23' coupled directly to the inlet port 11', and a breathing purier 132coupled in Aterms of gas ow between the gas ow junction 131and theconduit 23'. The conduits 20', 21' have conventional :rate of flowmeters 135, 136, respectively connected therein to regulate the ow ofgas in each of these conduits. Further control over these gas Hows isafforded by a manually operated needle valve 137 connected in conduit21' and by a needle valve 138 in conduit 20 ywhich permits a iiow ofcyclopropane therethrough in accordance 20` .ftheneedle Valve.

with the setting in adjustment of a control arm 139'for The cyclopropanein conduit 20 and the oxygen in conduit 21' ow into conduit 130 to beintermixed therein to form the input gas administered to the subject.This input gas has a relative percentage composition of pure anestheticgas and of oxygen gas wherein the relative percentages of these twocomponents are determined by the respective settings of the needlevalves 137 and 138. From rconduit 130 the input gas ows through junction131,;purifier 132, conduit 23,`inlet port 11', manifold 10', and adapter14' into the respiratory tract of the subject during inhalation thereby.

The outlet port 12' for the manifold has connected therewith asecondconduit means in the form. ofa conduit 40' running between theoutlet port and the gas oW junction 131. The output gas exhaled by thepatient -is conveyed by conduit 4b' from manifold 10' to junction 131from whence the output gas passes through the purifier 132 which is` acarbon dioxide absorber. The output gas after being freed of most of itscarbon dioxide content by passing through the purifier is recircuiatedback through conduit 23 to the subject. In this connection it will benoted that while there may be a considerable volume of circulating gas,the quantity of gas iiowing out of conduit 130 just balances with thequantity of gas which is inhaled and absorbed by the subject. Thus thereis a ow of input gas to the subject although this flow is accomplishedthrough the intermediary of a volurne of circulating gas.

To assure a proper gas circulation of the sort 'described, the apparatusis provided with valve means consisting of the check valve 140 disposedin conduit 23' to Vpermit gas iiow only toward inlet port 11' and `alsothe check valve 141 disposed in conduit 40' to permit gas ow in thisconduit only away from the outlet port12.

The apparatus,v of Figure 3 as so far described (with the exception ofthe mechanically adjustable needle valve 138) represents a closed circleanesthesia system such as is disclosed on page 24 of theafore-inentioned text by Otto Glasser. Such system is characterized bycontinuous circulation of the anesthetic gas around the loop formed byconduit 23', manifold 1d', conduit 40', and purilier 132. The fractionof oxygen `and cyclopropane l.absorbed by the subject from thecirculating anesthetic mixture during inhalation is continuouslyreplenished -yfrom the oxygen and cyclopropane flows in the conduits 21'and 20'. Further, in the circulating mixture, the 'waste productofcarbon dioxide exhaled by the subject `is`continuously removed by asoda lime mixture in 'the purifier :132. To permit closed loopcirculation of the `anesthetic mixture without the introduction ofpressure conditions varying widely from those normal for respiration,the described apparatus includes a accid balloon 145 connected to thepurier 132. As theV pressure in the circulating ,mixture rises andfalls, the balloon-145 1`l responsively expands and contracts to tend tomaintain the pressure at atmospheric value.

When a subject is under anaesthesia, the depth of anesthesia of thesubject at any time, although usually ascertained by indirect symptomsthereof such as rate of respiration or rate of heartbeat, is in fact indirect relation to the percentage content of anesthetic gas in the bloodstream of the subject. This blood stream content of anesthetic gas isreflected in the percentage of anesthetic gas appearing in the outputgas exhaled by the subject.

As in the case of the carbon dioxide content of the output gas in theFigure l apparatus, however, the content of anesthetic gas in the outputgas of the Figure 3 apparatus is characterized by a short termiuctuation in value over the period of each exhalation and by a trend ofthe uctuations from exhalation to exhalation. Of these two factors, onlythe trend in anesthetic gas content from exhalation to exhalation is asatisfactory indication of the depth of anesthesia of the subject.Accordingly in the operation of the Figure 3 apparatus, to automaticallybring the subject to or maintain the subject at a preselected depth ofanesthesia, it is necessary that the trend in this percentage content bedissociated from the short term uctuations therein.

To provide for automatic control of depth of anesthesia, the apparatusof Figure 3 includes a gas analyzer 42' connected in conduit 40 betweenthe outlet port 12' of the manifold and the mentioned gas flow junction13-1. The analyzer 42 may be an analyzer generally like the analyzer 42of the Figure l apparatus except that analyzer 42 is adapted to analyzethe output gas for a percentage content of cyclopropane rather than fora percentage content of carbon dioxide. It will be noted that theaforementioned text by Otto Glasser describes on page 1024 and on page1036 the details of analyzers suitable for both such purposes.

As is to be expected, cyclopropane analyzer 42' represents the outcomeof its analysis for this gas in the form of electrical signals.

The Figure 3 apparatus, like the Figure l apparatus includes anautomatic means responsive to the signals of the analyzer for adjustingthe regulator mechanism for the input gas to produce a preselectedbodily state of functioning of the subject. Thus in the present instancethe automatic means adjusts the setting of the adjustable needle valve138 to govern the relative percentages of cyclopropane and oxygeninjected into the circulating anesthetic mixture to thus bring thesubject to or maintain the subject at a preselected depth of anesthesia.This automatic means is analogous to that previously described for theFigure 1 apparatus in that it is comprised of the components of areference signal generating means 109', a subtracting chopper amplifier120', a power amplitier 121', the mentioned components being constructedand mutually cooperative in a manner alike to the correspondingcomponents of the Figure l apparatus. The automati-c means of the Figure3 apparatus differs, however, in one important respect, now to bedescribed, from the automatic means of the Figure l apparatus.

It will be noted in the Figure 3 apparatus that the conduit 40', whichserves among other uses to couple the cyclopropane analyzer 42 'inresponsive relation with the output gas, permits the free flow of outputgas during the Whole of each exhalation period by the subject. This freeflow of output gas in conduit 40 is preferable in a closed loopanesthetic administering system (of which conduit 40' represents asection of the loop) vin order to avoid the setting up of pressurestresses in the circulating anesthetic mixture as a result ofinterruption of the free circulation. It follows, however, that withfree flow of output gas through conduit 40 during the whole of eachexhalation, the output signals from analyzer 42 will also extend overthe whole of each a servomotor 122 and a phase shifter 126',

exhalation. Thus these analyzer signals will, as the unmodified outputof the analyzer, be indicative of both the intra-exhalation fluctuationsand the inter-exhalation trend in percentage content of anesthetic gasin the output gas, rather than being the desired indication of the trendin percentage content dissociated from the fluctuations thereof.

For the purpose of rendering the Figure 3 apparatus responsive primarilyto this trend in percentage content. the apparatus is provided with asampling means in the form of a pressure sensitive switch and a samplingrelay 151. Considering first the switch, this component comprises a gastight container 152, a resilient diaphragm 153 of electricallyconducting material dividing the interior of container 152 into lefthand and right hand gas tight chambers 154, 155, a contact 156 mountedon diaphragm 153, and a pair of fixed contacts 157, 158 respectivelylocated within chambers 154 and 15S to respectively close with contact156 when diaphragm 153 is in an expanded and a contracted condition.Normally diaphragm 153 is in contracted condition so that the contact156 of the diaphragm is electrically closed with the right hand xedContact 158.

For control of the expansion and contraction of diaphragm 153, theleft-hand chamber 154 of container 152 is connected by a conduit to ajunction 161 of this conduit with a section of conduit 40' betweenmanifold 10 and analyzer 42'. The right-hand chamber 155 of container152 is connected by a conduit 162 with the gas iiow junction 131. Duringthe major time interval of a respiration by the subject, the fluidpressure in conduit 40 at the junction 161 is either greater than orsubstantially equal to the fluid pressure at junction 131. Theserelative pressure conditions are duplicated by the relative conditionsof the pressures within chambers 154 and 155 to maintain diaphragm 153in contracted state to thus keep contact 156 closed with Contact 158. Atthe beginning of inhalation, however, the initial indrawing of breadthby the subject reduces the pressure at junction 161 below the pressureat gas junction 131, the mentioned pressure reduction being augmented bythe action of check valve 141 in preventing ow of gas from junction 131towards the other junction. The resulting pressure reduction in chamber154 of container 152, relative to the pressure in chamber 155 thereof,causes diaphragm 153 to expand so that contact 156 moves leftward tomomentarily close with contact 157. At this.time the output gas withinanalyzer 42 is that fraction of the output gas expelled by the subjectsubstantially at the end of exhalation. Of course, the describedmomentary pressure drop is speedily relieved by iiow of gas from conduit23 through manifold 10 into conduit 40', the diaphragm 153 hencerecontractng after a short interval to break the contact of elements156, 157 and to reestablish the contact of elements 156 and 158.

The contacts 156 and 153 are in a condenser charging circuit consisting,in series connection, of contact 156, the diaphragm 153, a capacitor165, a charging source shown as the battery 166, a resistor 167, and thecontact 158. When contacts 156 and 158 are closed, the condenser chargesup through the described circuit to output voltage value of the battery166. The contact 156 is also in a discharging circuit for capacitor 165,this discharging circuit consisting of the upper side of the capacitor,the diaphragm 153, contact 156, contact 157, a relay winding of samplingrelay 151, and a return through ground to the lower side of capacitor165. When contact 156 momentarily closes with Contact 157, thepreviously charged capacitor discharges through the circuit justdescribed to produce a momentary energization of relay winding 170. Thisenergization occurs at the beginning of inhalation when, -it will berecalled, the output gas within analyzer 42' is substantially ofendof-exhalation nature.

The relay winding 170 of sampling relay 151 operates 'gerente motor 122in its action of` adjusting needle valve 138 is thus made responsive tothe inter-exhalation trend" in the mentioned percentage content Aratherthan to the intraexhalation fluctuations thereof. From the foregoing theoperation `ot" the apparatus in Figure 3 will beilargely selfevident; IThe" reference signal generatingf means 109 provides a referenceY signalof a value representingla preselected depth of anesthesia for thesubject. If the subject isV or becomes under-anesthetized with respectto this depth, the resulting lack of cycl'opropane inthe blood stream ofthe patient will lie-manifested at the end of exhalationr by* a low orlowered percentage content of cyclopropane inthe output gas. YThis undervalue of cyclopropane has the effect, by the` respective actions of the;analyzer 42', the subtracting chopper amplier 120', the poweramplifer12,1, the sampling` relay 151 andthe servomotor 122', of producing asetting in adjustment of needlevalve` 138 to increase the ow ofcyclopropane through conduit 20 to thereby bring the subject to orrestore the subject to the preselected depth ofv anesthesia. In likemanner, if the subject is or becomes over-anesthetized, the excess ofcyclopropane in the blood stream ofthe subject initiates a` sequence ofevents in the operation of the apparatus which brings' the subject to or`restores' the subject to the preseiected depth of anesthesia.

1n the administration of anesthetic gases such as ethyl ether,chloroform and cyclopropane, which are essentially not consumed orchanged by the body, concentrations of such gases are usuallyadministered which the. patient may well tolerate until anesthesized tothe desired level, after which time the administration must be continuedat such concentrations so as to maintain an equilibrium between Vtheanesthetic input and anesthetic output. `The apparatus of this inventionmaintains the necessary equilibrium. For lirst plane anesthesiay(surgical), or slightly lighter, the following concentrations may `beused:

A rterial Plood, Conc. mgnL/lOO ce.

Substance Itf is assumed for such `concentrations to vcreate the 'desired equilibrium that the so-called Ventilation/ perfusion T4 aboveiorbelow that required' forv thesdesiredtanesthesia; the automatic meansresponds thereto and 'causes 7the needle valve to increase or decreasethe concentration of anesthetic in the input gas.- Theconcentrations oftypical anesthesia gases which, when present `in the output gas,fgivevarious depths of anesthesia are as follows:

Depth of Anesthesia Analgesic Light. Deep i Percent Percent PercentDethyl ether 5 1Q Chloroform 0.2 0. S 1: .3 Cyclopropanc 5 1:5 la Ethylchloride V' l ath 0.2 2 5 65 SO 0. 3 0.5 0. 8

When one of these gasesis administered an analyzer is used which iscapable of analyzing for the particular anesthetic gas administered.Thus, a chloroform anallyzer is usedwhen chloroform is administered, andan ethyl ether analyzer is used when ethyl ether is the anesthetic gasadministered.

In cases Where the anesthetic induces anethesia while the patientcontinues to breathe, as with cyclopropane, not only may theadministration to one patient of cycloy propaneV be regulated by thisinvention but, also, the

total volume exchange of respired gases. This is accomplished byanalyzing alternate exhalations for cyclopropane and either oxygen orcarbon dioxide. By

varranging'the apparatus in a suitable manner each exhalation say 'beanalyzedifor the content of both such gases. The sampling arrangementmay be set up as desired.

The above-described embodiments beingV exemplary only, it `will beunderstood that the present invention comprehends organizations dileringin form or detail Vfrom the presently described embodiments.Accordingly, the invention is not to be considered as limited save as isconsonant with the scope of the followingclaims,

I claim:

1. Apparatus for administering a respirable gas to a living subjectcomprising, a fluid flow system providing forfalternate ow of input andoutput gas to and from said'subject during the inhalations andexhalations there.- of, adjustable gas regulating mechanism connected insaid system in regulatingrelation with said input gas to therebyquantitatively control a bodily state offunctioning of said subject, gasanalyzer means connected in said systeni'in responsive relation withsaid output gas, said apparatus being adapted by automatically analyzingsaid V output gas to produce signals` indicative of the bodily reratiois about unity, i.e., there are no signicantportension isthefcontrolling determinant of the depth o f anesthesia Where theventilation/ perfusion ratio is about unity the anesthetic partialpressure in the input `gas is the controlling determinant of the depthof anesthesia. Where the ventilation/perfusion ratio is not `close tounity, the input concentration of the anesthetic gas must be raised inaccor-dance with the defect tor maintain the same arterialanestheticblood level.

Thel administration of an anesthetic gas is regulated by theconcentration of such gas in the outputgas or exhalation as determinedby the analyzer, which then signals the automatic means for adjustingthe needle valve for controlling input of the anesthetic gas. Theautomatic means is pre-set and controllable. lf the ,analyzer sponseofsaid subject to said input gas, and automatic means responsive to saidsignals for adjusting said regulatping' mechanism to render saidvbodilystate of functioning of said' subject accordant with a preselectedstandard therefor.

2. Apparatus as in claim 1 wherein said apparatus is a respiratorapparatus adapted to produce forced respiration of said subject. 3.Apparatus as iu claim 1 wherein said apparatus is an anaestheticadministration apparatus.

4. Apparatus for administering a respirable gas to a `living subjectcomprising, a uid ow system providing for alternate flow of input andoutput gas to and from said subject during the inhalations andexhalations thereof, adjustable gas regulating mechanism connected insaid system in regulating relation with said input gas to quantitativelycontrol a property thereof serving -to quantitatively control a bodilystate of functioning of said subject, gas analyzer means connected insaid system Vin responsive relation with said outputgas to automaticallyanalyze the same for a property thereof characterized in quantitativevaluegbyshorttetmfflucwatltlls and allonger term'trend, said uctuationsand Itrend being manifested, respectively, within individual exhalationsand from eX- halation to exhalation, and being, respectively, extraneousto and indicative of the bodily response of said subject to said inputgas, said analyzer means being adapted to generate signals as theoutcome of said analysis, sampling means operable by repetitivelysampling said fluctuations to render said analysis indicative in termsof said signals of said trend dissociated from said fluctuations, andautomatic means responsive -to said signals for adjusting saidregulating mechanism to produce a following by said trend of apreselected standard of value therefor, said apparatus being accordinglyadapted to automatically render said bodily state of functioning of saidsubject accordant with a preselected standard therefor.

5. Apparatus as in claim 4 wherein said sampling means establishes saidtrend by rendering said analysis indicative in terms of said signals ofan end-of-exhalation sampling of said output gas.

6. Apparatus for administering a respirable gas to a living7 subjectcomprising, a fluid fiow system providing for alternate flow of inputand output gas to and from said subject during the inhalations andexhalations thereof, adjustable gas regulating mechanism connected insaid system in regulating relation with said input gas to quantitativelycontrol a property thereof serving to quantitatively control a bodilystate of functioning of said subject, gas analyzer means connected insaid system in responsive relation with said output gas to automaticallyanalyze the same for a property thereof indicative of the bodilyresponse of said subject to said property of said input gas, saidanalyzer being adapted to generate signals indicative of the value ofsaid property of said output gas, means adapted to develop a referencesignal representing a preselected standard of value for said lastnamedproperty, means for comparing said analyzer signals with said referencesignal, and means responsive to a change established by said comparisonof said analyzer signals away from said reference signal for adjustingsaid regulating mechanism -to restore said analyzer signals toconformity with said reference signal, said apparatus being accordinglyadapted to automatically render said bodily state of functioning of saidsubject accordant with a preselected standard therefor. A

7. Apparatus for administering a respirable gas to a living subjectcomprising, a fluid ow system providing for alternate flow of input andoutput gas to and from said subject during the inhalations andexhalations thereof, adjustable gas regulating mechanism connected insaid system in regulating relation with said input gas to quantitativelycontrol a property thereof serving to quantitatively control a bodilystate of functioning of said subject, gas analyzer means connected insaid systemin responsive relation with said output gas to automaticallyanalyze the same during said respirations for a property thereofindicative of the bodily response of said subject to said property ofsaid input gas, said analyzer being adapted to generate electric voltagesignals indicative of the value of said property, of said output gas,electrical means for developing an electrical reference signal having asteady voltage representing a preselected value for said property ofsaid output gas, servo-amplifier means responsive to inputs of saidanalyzer signals and said reference signal for producing an output of anerror signal indicative of a change in voltage of said analyzer signalsaway from said reference signal, and servo-motor means responsive tosaid error signal for adjusting said regulating mechanism to restoresaid analyzer signals to equality with said reference signal by thecausal sequence described herein as following onV said adjustment, saidapparatus being accordingly adapted to automatically render said bodilystate of functioning of said subject accordant with a preselectedstandard therefor.

8. IApparatus as in claim 7 wherein said electrical means permitsadjustment between one value and an-l other of the steady voltage ofsaid reference signal,

9. Apparatus as in claim 7 wherein said servo-motor means is an electricmotor adapted to receive a first input of alternating current at a fixedphase and frequency, said servo-amplifier means is synchronized by saidcurrent to develop an alternating error signal at said frequency and ofopposite phases for oppositely `going changes of said analyzer signalsaway from said reference signal, and said motor is connected with saidservoamplifier to receive any error signal developed thereby as a secondinput to said motor, said motor being adapted to rotate in oppositedirections in the presence, respectively of alternating error signals ofopposite phases.

10. Apparatus for furnishing a living subject with respirable gas in thenature of input gas and output gas during, respectively, the inhalationsand exhalations of said subject, said apparatus comprising, a gasdistributing manifold having first and second ports, adapter means forguiding gas between said manifold and the respiratory tract of saidsubject, first conduit means connected with said first port to supplyinput gas through said manifold to said subject, an'adjustable gasregulating device connected in said conduit means 4to regulate saidinput gas to thereby quantitatively control a bodily state offunctioning of said subject, second conduit means connected with saidsecond port, a gas analyzer device connected in said second conduitmeans to receivev output gas from said subject by way bf said manifold,said analyzer device being adapted by automatically analyzing saidoutput gas to produce signals indicative of the bodily response of saidsubject to said input gas, and automatic means responsive to saidsignals for adjusting said regulating mechanism to render said bodilystate of functioning of said subject accordant with a preselectedstandard therefor. Y ll. Apparatus for furnishing a living subject withrespirable gas in the nature of input gas and outputgas during,respectively, the inhalations and exhalations of said subject, saidapparatus comprising, a gas distributing manifold having first andsecond ports, adapter means for guiding gas between said manifold andthe respiratory tract of said subject,'rst conduit means connected withsaid second port to supply input gas by way of said manifold to saidsubject, an adjustable gas regulating device connected in said conduitmeans to quantitatively control said input gas as to a property thereofserving to quantitatively control a bodily state of functioning of saidsubject, a gas analyzer device connected in said second conduit means toreceive said output gas from said subject by way of said manifold, saidanalyzer device being adapted to automatically analyze said output gasfor a property thereof characterized in quantitative value by short termfluctuations and a longer term trend, said fluctuations and trend beingmanifested, respectively, within individual exhalations and fromexhalation to eX- halation, and being, respectively, extraneous to andindicative in degree of the bodily response of said subject to saidproperty of said input gas, said analyzer being further adapted togenerate electric signals as the outcome of said analysis, a samplingdevice operable by repetitive- .ly Sampling said fluctuations to rendersaid analysis indicative interms of said signals of said trend dissociated from said uctuations, electrical means for developingan electricalreference signal representing a preselected standard of value for saidproperty of said output gas, a servo-amplifier responsive to inputs ofsaid analyzer signals and said reference signal for producing an outputof an error signal indicative of change in said analyzer signals awayfrom said reference signal, and servo-motor means responsive to saiderror signal for adjusting said lregulating vmechanism to produce arestoration of said analyzer signals with said reference signal bythecausal sequence described herein as following on said adjustment,said apparatus being accordingly adapted to render ,said bodily state offunctioning of said subject accordant with a preselected standardtherefor.

12. Apparatus for furnishing a living subject with respirable gas in thenature of input gas and output gas Y .fr-,cinese manifold having nrstand' second ports, adapter means for guiding 'gas between said manifoldand the respiratory tract ofsaidfsubject, rst conduit 'meansconnectedwith said iirst port to supply input gas by way of said manifold tosaid' subject, an adjustable gas regulating device connected in saidrstconduitmeans to quantitatively control said input gas as to` a propertythereofserving-to quantitatively control a bodilystateof'functioningof'said subject, second conduit means connected Withsaidsecond port, a gas 'analyzer device 'connected in said second conduitmeans tol receive said output gaefromy said subject by way of saidymanifold, said 1analyzer devicebeing adapted-torautomatically analyze4said output gas for a property 'thereof characterizedv in` quantitative`value by short termv uctuations and a-longer term trend, said uctuatonsand trend being manifested, respectively,

within individual exhalations and from exhalation to exhalation, andbeing, respectively, extraneous to and indic ative of the bodilyresponse of said subject to said property of said input gas, saidanalyzer being further adapted to generate electric signals as theoutcome ofsaid analysis, a sampling device operable in timed relationwith changeover in respiration of said subject from exhalation toinhalation for rendering said analysis indicative in terms of saidsignals of an end-of-exhalation sampling of said output gas for saidproperty thereof, said sampling means thereby rendering said signalsindicative of said trend dissociated from said fluctuations, electricalmeans for developing an electrical reference signal having a steadyvoltage representing a preselected value for said property of saidoutput gas, a servo amplifier responsive to inputs of said analyzersignals, said reference signal, and an alternating chopping signal ofxed frequency and phase for producing an output of an'alter nating errorsignal of said frequency and of opposite phases when said analyzersignals change in one and the other direction away from said referencesignal, and an electric motor mechanically coupled with said regulatordevice to adjust the same, electrically coupled with said amplifier toreceive said error signal as one input, and

electrically coupled to receive an alternating current of said frequencyand of xed phase as another input, said motor being respectivelyresponsive to error signals of opposite phases to produce oppositedirection adjustments of said regulator device serving to equalize saidanalyzer signals with said reference signal, said apparatus beingaccordingly adapted to automatically render said bodily state offunctioning of said subject accordant with a preselected standardtherefor.

13. Apparatus for administering respirable gas to a living subjectcomprising, la source of input gas under pressure, a manifold having aninlet port and an outlet port, adapter means for guiding the flow of gasbetween said manifold and the respiratory tract of said subject, firstconduit means disposed between said source and said inlet port to supplyinput gas to said manifold, valve means for opening said inlet port,timing means for `actuating said valve means to open said inlet portintermittently to thereby induce respirations in said subject consistingof Ialternate inhalations of input gas responsive to the pressurethereof, and of exhalations of output gas, an adjustable pressureregulator for said input gas disposed in said conduit means between saidsource and said inlet port, second conduit means connected with saidoutlet port, an analyzing device connected in said second conduit meansand adapted to provide electric signals as` a lfunction of the carbondioxide content of said output gas, sampling means connected in saidsecond conduit means between said manifold and said analyzing device,

r`18 matie means .responsivejtofsaid signal for adjusting said;regulatorio maintain it preselected depth of respiration for saidsubject; Y

14. Apparatus for administeringianaestlieticto aliv-y ing subjectcomprising, a manifoldY having ati-"inlet port and an outlet port,adapter means for guiding gas'between said manifold' and the respiratorytract of 'said subject, first conduit means comprised both of a'y pairof conduits respectively adapted Vtocarry. anaesthetic gas and oxygenand of aithird'conduit connected 'between said inlet port andboth ofsaid pair of'foondu'its'to rniJt` said anaesthetic gas andfox'ygen, theintermixture there-f` of being the input gas for saidjsubject,-an`adjustable regulator connected in said'conduit carrying anaesthetic gasto meter the amount thereof'owing to saidthird conduit to vtherebycontrol-the percentage"thereofI present in said input gas, secondconduit? meansfconnectedwith said outlet port,kvalve means for directinginto said second conduit means the ow of output gasfrom said subjectinto said manifold, an analyzer device connected in said second conduitmeans to generate electric voltage signals as a function of the contentof anaesthetic gas in said output gas, electric circuit means adapted todevelop a steady reference voltage representing a preselected depth ofanaesthesia for said subject, servo-amplifier means responsive to`inputs of said analyzer signals and said reference signal to develop anoutput of an error signal indicative of change in said analyzer signalsaway from said reference signal, switch means responsive to the pressuredrop in said manifold during changeover in the respiration of saidsubject from exhalation to inhalation to close a circuit for said errorsignal as a consequence of said pressure drop, said error signal beingthus rendered indicative of an end-of-exhalation sampling from thepatient and gas analysis means directly com-v municating therewith foranalyzing the undiluted exhalations from the patient, and means actuatedby the gas analysis means for controlling the means for administeringthe chemicalto the patient.

16. Apparatus comprising means for administering a therapeutic treatmentto a patient, means for directly receiving exhalations from the patientand gas analysis means directly communicating therewith for analyzingthe yundiluted exhalations from the patient, and means actuated by thegas analysis means for controlling the means for administering thetherapeutic treatment to the patient.

R17. Apparatus comprising means for supplying an inhalation gas to apatient, means for directly receiving `exhalation from a lung of thepatient and gas analysis means directly communicating therewith foranalyzing theundiluted exhalations fromv the patient, and means actuatedby the gas analysis means for controlling the means for supplying theinhalation gas to the patient.

18. Apparatus comprising means for supplying an r`inhalation gas to apatient, means for directly receiving exhalations from a lung of apatient and gas analysis said sampling means being controlled by saidtiming means'to draw oi a sample of the output gas present in saidmanifold at the end of exhalation and to thereafter discharge saidsample into said analyzer means, and automeans directly communicatingtherewith for analyzing the undiluted exhalations from the patient, andmeans actuated by the gas analysis means for automatically controllingthe means for supplying the inhalation gas toY `regulate the compositionof the inhalation gas to the patient.

` 19. Apparatus comprising means for supplying an inhalation gas to apatient, means for directly receiving exhalations from a lung of apatient and gas analysis means directly communicating therewith for.analyzing:v

the undiluted, exhalatidns-,fromfthe patient, andmeans actuated by thegas analysis means for controlling the meansfor`supplying;the-inhalation gas to regulate the compositionof aninhalation gas to the patient. H

r2 0. Apparatus comprising means for supplying an 2l; The apparatus ofclaimvZO in whichthe gas ana-v lysis means analyzes cyclopropane. Y

22.. Apparatus comprising means .for administering a therapeutic gas toapatient, means for directlyreceiving exhalationV from fal unlg of thepatientand-.gas analysis.;

means directly communicatingl therewith for analyzing the` undilutedyexhalation from lthepatient, ,and means actuated by the gas analysismeans vfor controllingy the means forsupplying'the therapeutic gas sothat admnistration of the therapeutic gas may be regulated.v

23. The apparatus of claim 22 in whichv the gas analysis means analyzescarbon dioxide. y

24. The apparatus of claim 22 in which the gas an- 1D alysis meansanalyzes oxygen.

References Cited in thcile of this patent UNITED STATES 'PATENTS2,754,819 Kirschbaum. ..v- July f 17, 1956 j UNlTED STATES' PATENT FFTCECERTIFICATE OF CORRECTION Patent No. 2915O56 December 1q 1959 Arnold S.L Lee It is herebr certified that error appears in theprintedspecification of the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 5-q` line 30(I for "713" read' 77a wline 31l for 77a readl 71acolumn 'Xq line 57., for "photomer" read m photometer eg column SQ. line20,? for `"carbide" read M4 carbon wm; line 36(I for "351921" read m351921) ma.

Signed and sealed this 23rd day of August 1960.

( SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

